The Maasai Herbalists in Arusha Town, Tanzania     

Fouad Ibrahim  Barbara Ibrahim 《GeoJournal》1998,46(2):141-154

This paper presents the findings of a case-study carried out on the Maasai herbalists of Arusha town, whose social and economic situation, both in their villages of origin and in town is being analysed. Special emphasis is laid on the struggle of women herbalists to upgrade their low economic and social status in their home villages and, at the same time, satisfy their most basic needs in town. In this, they depend on their asset of indigenous ethnomedical knowledge, which they commercialise. They do not consider themselves professional experts among their own people, but they become ones when they are in town. A major aim of this paper is also to illustrate the wealth of indigenous knowledge concerning the biodiversity of people's environment. A survey of the medical plants most frequently sold by the herbalists is presented with the intention of identifying those species which are endangered, although the herbalists themselves do not yet perceive the seriousness of the situation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Significance of the Virus-Rich 2–200 nm Size Fraction of Seawater for Heterotrophic Flagellates: I. Impact on Growth     

Barbara F.  Pesan  Markus G.  Weinbauer Peter  Peduzzi 《Marine Ecology》1994,15(3-4):281-290

Abstract. The effect of artificially changing the concentration of naturally occurring free virus-like particles (VLPs) on growth of marine heterotrophic flagellates was tested in batch cultures using ultrafiltration technology. This manipulation influenced the course of flagellate growth markedly. During 1 week of incubation the growth of 4 tested flagellate strains ( Oxyrrhis marina, Paraphysomonas imperforata, Petalomonas cantuscygni, Pteridomonas danica ) was strongly favoured after increasing the VLP concentration. Bacteria, however, were repressed in these treatments beyond 50 h. In cultures with natural seawater microbiota, we both reduced and enriched the concentration of VLPs. In these cultures, reduction of material in the virus-rich 2–200 nm size fraction led to a strong positive growth response of heterotrophic flagellates. In VLP-enriched treatments of natural seawater microbiota a tendency toward growth stimulation was also found, although this was not significant. Enrichment with VLPs caused no recognizable mortality either in cultured flagellate strains or in naturally occurring flagellate communities. However, it is suggested that a highly bioactive component must be present in the virus-rich 2–200 nm size fraction. Virus-like particles are discussed as possible candidates influencing heterotrophic flagellate community successions.  相似文献   

Effect of siderophores on the light-induced dissolution of colloidal iron(III) (hydr)oxides   总被引：1，自引：0，他引：1  

Paul M. Borer  Barbara Sulzberger  Petra Reichard  Stephan M. Kraemer   《Marine Chemistry》2005,93(2-4):179-193

Siderophores play an important role in biological iron acquisition in iron-limited aquatic systems. While it is widely accepted that the solubilization of iron-bearing mineral phases is a key function of siderophores, the mechanism of siderophore-promoted mineral dissolution in aquatic systems is largely unknown. In this study, we investigated the effect of siderophores (desferrioxamine B (DFOB) and aerobactin) on light-induced dissolution of goethite and lepidocrocite in the presence or absence of oxalate in aerated and deaerated suspensions at pH 6. For the irradiated two-ligand system (oxalate/siderophore), the experimental results suggest that oxalate acts as the electron donor for the formation of surface Fe(II), and the siderophore acts as an efficient shuttle for the transfer of surface Fe(II) into solution. Furthermore, even in the absence of an electron donor such as oxalate, both DFOB and aerobactin accelerated the light-induced dissolution of lepidocrocite as compared to the thermal dissolution. Experiments with dissolved Fe(III)–DFOB and Fe(III)–aerobactin complexes suggest that this enhancing effect is not due to photolysis of corresponding surface complexes but to efficient transfer of reduced surface Fe(II) into solution, where surface Fe(II) may be formed, e.g., through photolysis of surface Fe(III)–hydroxo groups. Based on this study, we conclude that the interplay of light and siderophores may play a key role in the dissolution of colloidal iron(III) (hydr)oxides in marine systems, particularly in the presence of efficient electron donors.  相似文献   

Solubility of Fe-ettringite (Ca₆[Fe(OH)₆]₂(SO₄)₃ · 26H₂O)     

Göril Möschner  Barbara Lothenbach  Andrea Ulrich  Ruben Kretzschmar 《Geochimica et cosmochimica acta》2008,72(1):1-18

The solubility of Fe-ettringite (Ca₆[Fe(OH)₆]₂(SO₄)₃ · 26H₂O) was measured in a series of precipitation and dissolution experiments at 20 °C and at pH-values between 11.0 and 14.0 using synthesised material. A time-series study showed that equilibrium was reached within 180 days of ageing. After equilibrating, the solid phases were analysed by XRD and TGA while the aqueous solutions were analysed by ICP-OES (calcium, sulphur) and ICP-MS (iron). Fe-ettringite was found to be stable up to pH 13.0. At higher pH-values Fe-monosulphate (Ca₄[Fe(OH)₆]₂(SO₄) · 6H₂O) and Fe-monocarbonate (Ca₄[Fe(OH)₆]₂(CO₃) · 6H₂O) are formed. The solubilities of these hydrates at 25 °C are:   相似文献   

An Observational Case Study on the Influence of Atmospheric Boundary-Layer Dynamics on New Particle Formation     

Andreas Platis  Barbara Altstädter  Birgit Wehner  Norman Wildmann  Astrid Lampert  Markus Hermann  Wolfram Birmili  Jens Bange 《Boundary-Layer Meteorology》2016,158(1):67-92

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Pastoralists in transition — a case study from Lengijape,Maasai Steppe     

Barbara  Ibrahim Ibrahim  N. Fouad 《GeoJournal》1995,36(1):27-48

The change of the Maasai from pure pastoralists to agropastoralists has brought about serious problems for them. This paper tries to analyse this process of change and to throw some light on the resultant problems. First, it is being shown how the climate of the Maasai Steppe is too dry for a successful cultivation of maize by them, which has become their main food. Successive crop failures and high labour costs have rendered maize-growing a losing-business for the Maasai. Moreover, the State policy of granting certificates of occupancy in the Maasai land to outsiders allowing them to make large-mechanized farms, has alarmed the Maasai so much that many of them rushed back to their home areas to rescue their land from being grapped by other ethnic groups. Thus, they began to abandon their traditional grazing-movements, which are highly adapted to the ecological conditions of the Maasai Steppe. At the same time, the herds of the Maasai were decimated, because of the spread of animal diseases following the deterioration of the State veterinary service system. Added to this are the losses incurred through distress sales of cattle for buying maize for food, at a time at which the maize prices are increasing at a much higher rate than the prices of livestock. This dilemma of the Maasai and their indigenous coping mechanisms are being illustrated by the case of the people of Mokia at Namalulu, with special consideration of the role of women in solving these problems.  相似文献   

Marine pollution research in South East Asia     

Barbara E. Brown 《Marine pollution bulletin》1985,16(3):95-97

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Relationships Between Ground-Water Silica, Total Dissolved Solids, and Specific Electrical Conductivity     

Barbara A. Day  Harry I. Nightingale 《Ground water》1984,22(1):80-85

Specific electrical conductivity (SEC), total dissolved solids (TDS), and silica (SiO₂) are ground-water quality parameters routinely measured in a laboratory. Electrical conductivity measurements are made quickly and are less costly than TDS measurements. Once the relationship between the parameters is determined by regression analysis, TDS can be estimated quickly from the SEC and SiO₂ measurements. Water quality data from 25 city wells in Fresno, California, and historical ground-water quality data from the adjacent San Joaquin River/Kings River alluvial interfan (central San Joaquin Valley, California), the Kaweah River alluvial fan, and the Kern River alluvial fan (southern San Joaquin Valley) were used in this investigation. For the specific hydrologic areas studied, the model's TDS predictive ability is improved when SiO₂ is included with SEC as the independent variables.  相似文献   

Reflection of the orographic patterns in the micro- and mesoclimatic conditions     

Barbara Obrebska-Starkel 《GeoJournal》1984,8(3):259-263

In the Polish Carpathian Mountains two altitudinal profiles were chosen. Ranging from 200 to 1,000 m asl along 20°00 and 21°30E their spatial patterns of the topographical types in the mountains and uplands, geometric configuration of concave topographies and direction of their course are different.The effects of topography on the mesoclimatic conditions in the area investigated were analyzed by the diurnal air temperature records at the 28 meteorological stations in the years 1951 – 1970. Along the two profiles, taking the points situated at the same height asl and similar altitude, the mean extreme temperatures in the particular months, as well as the values of the first and ninth deciles of the maximum and minimum temperatures were analyzed. Special consideration was given to the spatial distribution of the minimum temperature and characteristics derived, because it reflects the influence of topography in a higher degree than the maximum temperature. Since low air temperatures are the main factor for the plant growth in the Polish Carpathians, spatial differentiation of the minimum temperature regulates the rate of development of the wild and cultivated plants during the growing season.  相似文献   

Thermal asymmetry and cross-valley circulation in a small alpine valley     

Barbara Hennemuth 《Boundary-Layer Meteorology》1986,36(4):371-394

Wind observations from a small Alpine valley are used to investigate the problem of cross-valley winds. The observed daytime windfield is a superposition of dynamically and thermally forced cross-winds. Prevailing cross-winds above the valley result in a recirculation cell above the lee slope. The return flow is strengthened or weakened by thermal effects which induce a wind that blows from the shaded to the sunny side of the valley. The reaction time of the thermally induced cross-winds is only 4 min. The horizontal and vertical motions of the cross-valley circulation transport heat in such a way that the insolation differences between the two sides of the valley are nearly equalized.  相似文献